The massacre of more than 130 Pakistani school children by Taliban gunmen was a chilling reminder of Hillary Clinton's warning to Islamabad in 2011 that "you can't keep snakes in your backyard and expect them only to bite your neighbors".

Now, as Pakistan reels in horror at the bloodshed in a military-run high school in Peshawar city on Tuesday, pressure will mount on politicians and generals who have long been tolerant of militants they counted as strategic assets in their rivalry with India and jostle for influence in Afghanistan.

"There have been national leaders who been apologetic about the Taliban," said Sherry Rehman, a former envoy to Washington and prominent opposition politician. "People will have to stop equivocating and come together in the face of national tragedy."

Outrage over the killing of so many children is likely to seriously erode sympathy for militants in a country where many people have long been suspicious of the U.S.-led "war on terror", and spur the army to intensify an offensive it launched this year on havens in mountains along the Afghan border.

Army chief Raheel Sharif has already signaled that retaliation would follow. On Wednesday, Mubasher Lucman, a prominent host on the ARY news channel, Tweeted: "Enough time already. Tell Air Chief to initiate carpet bombing".

"The Taliban may be trying to slacken the resolve of the military by suggesting that there could be a tremendous human costs to the military offensive and create public pressure on the military to back off from this offensive," said Vali Nasr, dean of the Johns Hopkins University School of Advanced International Studies.

"But it may actually ricochet on them," said Nasr, formerly a State Department adviser on Afghanistan and Pakistan.

Pakistan's Taliban, whose nominal unity has frayed this year with the emergence of competing factions, are distinct from the Afghan Taliban. But the groups are linked, and share the goals of toppling their respective governments and setting up a strict Islamist state across the region.

PRESSURE ON GOVERNMENT

Widening the offensive against the Pakistan Taliban could include "hot pursuit" by the military across the porous border into Afghanistan, where many Pakistani militants hide. That could put at risk a recent rapprochement between Islamabad and Kabul.

Pakistan's Dawn newspaper quoted a source as saying that the school attackers were acting on orders from handlers in Afghanistan.

"They have been asking the Afghan government to do something about this for a very long time ... Pakistan may be left with no other option – the brutality of the attack demands a response," said Saifullah Mehsud, head of the FATA Research Center in Islamabad, referring to the Peshawar carnage.

Despite the risks, public outrage means the army now has a freer hand to go after the Taliban, entrenching its dominance over a government that pursued fruitless peace talks with the militants and offered only half-hearted support for a military offensive.

The civilian government is already on a backfoot, weakened by months of street demonstrations led by opposition leaders calling for the resignation of Prime Minister Nawaz Sharif. Now, it will come under pressure to fall in line with the military.

"Pakistan's political leadership needs to make a clear choice to fight the Taliban decisively, not with half measures," said Bruce Riedel, a former senior CIA and White House counter-terrorism official, now the Brookings Institution think-tank.

"The burden is on Prime Minister Sharif to show he can unite the country to defend its children," he said.

Pakistan has for years nurtured militants in the belief they could be valuable fighters in the event of war with a much bigger Indian army. But some factions turned on government forces after Islamabad signed up to the U.S.-led campaign against militancy following the Sept. 11, 2001, attacks.

Even if the army and government close ranks on the need to hit back and tighten security in the country's cities, however, the military and its powerful intelligence arm are likely to cling to the notion of "good" Taliban.

An Indian official, who has dealt for years with New Delhi's policies in the region, said that with NATO troops leaving Afghanistan, the Pakistani military would leave unhindered the Haqqani network that strikes inside Afghanistan from Pakistan and the Lashkar-e-Taiba group that fights Indian rule in Kashmir.

"The Pakistan army has adhered to its longstanding doctrine of distinguishing between terrorist groups that are engaged in hostilities with it and those who are willing to act as its proxies whether in Afghanistan and India," said Vivek Katju, a former Indian ambassador to Afghanistan.

"Pakistan ... cannot run with the hare and hunt with the hound," he wrote in India's Economic Times.